Field of the Invention
The present invention relates to golf balls.
Description of the Related Art
For golf balls, in addition to flight performances, approach performances and spin stability have been demanded. Golf balls having favorable approach performances are accompanied by a great backspin rate upon approach shots. Golf balls that are superior in the spin stability are less likely to be accompanied by variance of the backspin rate. In the golf balls that are superior in spin stability, for example, the difference between dry spin rate Sd and wet spin rate Sw is small. The ratio (Sw/Sd) is also referred to as spin retention, which has been employed as a marker of the spin stability. In particular, high-level golf players tend to place a high priority on approach performances, and spin stability upon approach shots. The dry spin rate Sd means backspin rate in a dry state, while the wet spin rate Sw means a backspin rate in a wet state. The wet state refers to any state in which ball and/or club face get wet with water.
Specifications of coating films (paint layers) can affect the performances of golf balls. In order to improve characteristics of golf balls, golf balls in which thickness and the like of the coating film have been considered were proposed. Japanese Unexamined Patent Application, First Publication No. 2003-265650 (United States Patent Publication No. 2003/176242A1) discloses a golf ball having a favorable spin retention, in which the thickness of the coating film, the 50% modulus of the coating film, and the ratio of the thickness of the coating film and the thickness of the cover are defined. Japanese Unexamined Patent Application, First Publication No. 2000-176047 (U.S. Pat. No. 6,488,596) discloses a golf ball that is excellent in scuff resistance in which the coating film is from 5 to 20 micron. Japanese Unexamined Patent Application, First Publication No. Hei 9-276445 (U.S. Pat. No. 5,902,190) discloses that design freedom of golf balls can be increased by providing a coating film having a thickness of 50 to 700 μm. Japanese Unexamined Patent Application, First Publication No. Hei 8-322961 (U.S. Pat. No. 5,695,414) discloses a golf ball in which the proportion of the depth of the dimple and the average thickness of the coated film that covers the dimple is defined.